1. Field of the Invention
The present invention relates to a dielectric element and a piezoelectric (electrostrictive) element capable of applications as MEMS in particular, such as a capacitor, a sensor, a transducer and an actuator as well as an ink jet head and an ink jet recording apparatus using the piezoelectric element. The present invention further relates to a manufacturing method thereof.
2. Related Background Art
While a dielectric material of a high dielectric constant as a capacitor is in demand, thinning of ceramics materials such as BaTiO3 is underway for the sake of miniaturizing the capacitor. However, the dielectric constants of the ceramics materials such as BaTiO3 and Pb (Zr, Ti)O3 are only 1500 or so, and they often become electronic devices of defective characteristics when problems of improper sintering and a deficient structure of an interface are further added thereto by thinning them.
As for a piezoelectric, researches in the fields of MEMS and piezoelectric applications are widely conducted in recent years so that a thin-film piezoelectric element of good characteristics is expected. The piezoelectric element is an element that expands and contracts when having its piezoelectric layer sandwiched by electrodes and having an electric field applied thereto, and is adaptable to a motor, an ultrasonic motor, an actuator and so on.
Materials mainly used in the application fields are PZT materials which were discovered about 50 years ago. Sintering temperature of the PZT materials is over 1100° C., and so material development is underway by using a sol-gel method, a sputter technique, an MBE method, a PLD method, a CVD method and so on in order to adapt them as a thin-film element. In the case of applying them as a thin film, however, there may be a problem that physical destruction in a film or on a film interface is apt to occur. For that reason, attempts are made to devise a crystal structure of the piezoelectric layer so as to obtain a large piezoelectric constant and good pressure tightness. An example of using an orientation film by sputtering (001) as an ink jet head is described in Japanese Patent Application Laid-Open No. H08-116103. This method provides oriented electrodes on a substrate, and controls a crystal structure of a piezoelectric film by having a PbTiO3 layer with no Zr intervening between the piezoelectric film and the electrodes. However, this method has a problem that the dielectric constant of the PbTiO3 layer is lower than that of PZT of the piezoelectric film and so electric field intensity applied to a PZT layer becomes lower in the case of applying the electric field.
To realize a piezoelectric constant exceeding PZT ceramics, single-crystallization of relaxer materials has been studied, and a single-crystal substance in bulk has been obtained by a fusion method with a large piezoelectric constant thereof reported. A report on these thin-film-formed relaxer materials was made at FMA (Ferroelectrics Meeting of Application) in 2002. However, it is not a status in which the large piezoelectric constant can be obtained in a stable state. U.S. Pat. No. 5,804,907 describes use of a relaxer single-crystal material as the actuator. However, it has the problems that a method of creating the element is not concretely described and that the single-crystal material is created by the fusion method (TSSG method) and so a thin film of 50 μm or less cannot be handled.